In modern motor vehicles, use is made of camshaft adjustment systems which can control the valve opening times of internal combustion engines. The valve opening times are controlled via a camshaft. The camshaft is composed of “cams” which are fitted on a shaft. When the shafts rotate, the cams come into contact with, for example, a valve lever such that the latter opens the valve in order therefore either to conduct a fuel mixture into the cylinder of an internal combustion engine or, after the combustion process, to conduct the exhaust gases out of the cylinder.
The valve opening times are determined via the arrangement of the cams and via the speed of rotation of the camshaft. The camshaft is usually coupled for driving to the crankshaft of the internal combustion engine. If the connection between the camshaft and the crankshaft comprises a fixed, unchangeable connection, the valve opening times already have to be determined at an early construction stage of the engine. A subsequent adjustment of the valve opening times during operation of the engine is no longer possible.
In order to make this possible, use is made of camshaft adjustment systems which make it possible to control the valve clearance even during operation of an engine. One possible realization of a camshaft adjustment system is implemented by a hydraulic controller DE 10 2004 019 190. In order to transmit force, a driven part or rotor element, which is fitted in a rotationally fixed manner, is fastened to the end of a camshaft and is designed in order to transmit force to a driving wheel or stator element connected in a rotationally fixed manner to the crankshaft. Rotation of the driving wheel and of the driven wheel in a specific manner therefore makes it possible to adjust the valve opening times between the crankshaft and the camshaft.
In order to realize this relative change in the phase position between the camshaft and crankshaft, the phase can be ensured via hydraulic camshaft adjustment systems. In a pressure chamber, wings fitted in a rotationally fixed manner to the driving part form a first and a second pressure chamber. The relative position of the camshaft to the crankshaft can be adjusted in accordance with the ratio of the pressure level of the first and second pressure chambers. However, if hydraulic pressure is absent, the camshaft has a considerable amount of play, since the wings can move freely in the pressure chambers. In addition, the hydraulic oil pressure is generally built up by a motor vehicle pump which provides the hydraulic pressure as a function of rotational speed. If the oil pressure abruptly ceases, as, for example, in the event of the engine stalling or during starting operations of an engine, it is important to fix the camshaft in a fixed ratio to the crankshaft.
For this purpose, use is made of “locking pins” which are located in bores of the rotor element. The locking pins comprise a sleeve into which an extendable part can retract and extend by means of a spring. If the oil pressure ceases, the spring force causes the locking pin to extend and reach into the cutouts, for example, of a closure cover, thus preventing play between the camshaft and crankshaft.